JP2005509359A - Method for selecting a subset of antennas from multiple antennas in a diversity system - Google Patents

Abstract

Described is a method of selecting a subset of N out of N antennas by, starting from a hypothetical set of N antennas, removing (N-N) times an antenna from the hypothetical set such that a capacity of the hypothetical set after removal of the antenna has a maximum value. The subset of N out of N antennas corresponds to the remaining hypothetical set of N antennas. The method is computationally efficient and can advantageously be used in a transmitter (12) having M transmit antennas (16) and M transmit chains (20), M>M, to select a subset of M transmit antennas (16) which, when coupled to the M transmit chains (20), can transmit M signals with a near-optimal transmit capacity. Similarly, the method can be used in a receiver (14) having N receive antennas (22) and N receive chains (26), N>N, to select a subset of N receive antennas (22) which, when coupled to the N receive chains (26), can receive N signals with a near-optimal receive capacity.

Description

The present invention relates to a method of selecting a subset of N in the N antennas for receiving / transmitting N signals.

The present invention further relates to a receiver for receiving N signals, N is greater than N, and the receiver has N receive antennas and N receive chains, to transmit M signal a transmitter, M is greater than M, and the transmitter having M transmit antennas and M transmit chains, N is greater than N, the reception with N receiving antennas and N receive chains a method of receiving N signals by vessel, M is greater than M, and to a method of transmitting M signals by the transmitter with M transmit antennas and M transmit chains.

  Such a method is known from the document “Hybrid selection / optimum combining” by Jack H. Winters and Moe Z. Win, Proceedings Vehicular Technology Conference, Rhodes, May 2001. In modern transmission systems, the transmitter / receiver can be equipped with multiple transmit / receive antennas to efficiently communicate information. The number of physical transmit / receive antennas may be greater than the number of available transmit / receive chains (eg, the number of digital inputs / outputs). In such a case, only a subset of the available transmit / receive antennas can be used simultaneously. This subset can be optimized by the channel between the transmitter and the receiver, i.e. by channel information that may be available at the receiver and / or transmitter. From the above document, the use of more antennas than the actual transmit / receive chain by adaptive selection of the active subset of antennas with channel information can lead to a substantial increase in the capacity of the radio channel.

  Known methods for selecting a subset of antennas are computationally inefficient. This entails a thorough investigation to obtain the best subset, i.e. the subset that gives the optimum capacity (throughput) of the channel. The number of computations required for such a brute force approach increases exponentially with a linear increase in the number of antennas and becomes infeasible even for a moderate number of antennas.

  It is an object of the present invention to provide an introductory method that results in a computationally efficient but still substantially optimal subset, i.e. a subset that provides a substantially optimal communication capacity.

This object is achieved by the process according to the invention, the method, starting from the assumption set of N antennas, a step of removing (N -N) times an antenna from the hypothetical set, the removal Comprises the steps performed such that the capacity of the hypothetical set has a maximum after removal of the antenna, the subset corresponding to the remaining hypothetical set of N antennas. The present invention starts with a hypothetical set of N antennas, with a substantial reduction in computational complexity, after which one ( N -N) antennas are removed from the hypothetical set, thereby Based on the recognition that for each stage that an antenna is removed, the removal of the antenna can be achieved by causing a minimum reduction in the capacity of the subset of antennas corresponding to the hypothetical set. Note that only a single antenna is removed at each stage. Starting from a hypothetical set of N antennas, ( N −N) antennas are subsequently removed until a hypothetical set of N antennas remains. This remaining hypothetical set of N antennas corresponds to the desired subset of N antennas. This subset of N antennas can then be combined into N available receive / transmit chains. Simulations have shown that this approach leads to the selection of a subset that gives a capacity very close to the optimal capacity of the known method.

  The above objects and features of the present invention will become more apparent from the following description of preferred embodiments with reference to the accompanying drawings.

  In the figures, identical parts are given the same reference numerals.

FIG. 1 shows a block diagram of a transmission system 10 according to the present invention. The transmission system 10 includes a transmitter 12 and a receiver 14. The transmission system 10 may further include a plurality of transmitters 12 and a plurality of receivers 14 (not shown). The transmitter 12 includes a plurality of M transmission antennas 16 and a plurality of M transmission chains 20. FIG. 1 merely illustrates one embodiment of a transmitter 12 where M is 5 and M is 2. Other values of M and M, M can be as long as greater than M. The transmitter 12 further comprises coupling means 18 for selectively coupling the two transmission chains 20 to a subset of two of the five transmit antennas 16. Coupling means 18, starting from the assumption set of M antennas, the antenna from the hypothetical set to (M -M) times removed, the removal capacity of the hypothetical set after removal of the antenna up to It is configured to select a subset of M antennas 16 by being performed with values. Finally, the desired subset corresponds to the remaining hypothetical set of M antennas. Due to the coupling of the two transmit chains 20 to the two transmit antennas, the transmitter 12 can transmit two (M) signals to the receiver 14 via a (wireless) channel. Each transmit chain 20 may have a conventional RF front end that may include a digital to analog converter, one or more amplifiers, one or more filters, and a mixer.

The receiver 14 includes a plurality of N reception antennas 22 and a plurality of N reception chains 26. FIG. 1 merely illustrates one embodiment of a receiver 14 where N is 4 and N is 2. Other values of N and N, N can be as long as greater than N. The receiver 14 further comprises coupling means 24 configured to selectively couple the two receive chains to a subset of two of the four receive antennas 22. Coupling means 24, starting from the assumption set of N antennas, the antenna from the hypothetical set (N -N) times removed, the removal capacity of the hypothetical set after removal of the antenna up to It is configured to select the subset of N antennas 22 by having a value. Finally, the desired subset corresponds to the remaining hypothetical set of N antennas. Due to the coupling of the two receive antennas 22 to the two receive chains 26, the receiver 14 can receive two (N) signals from the transmitter 12 via a (wireless) communication path. Each receive chain 26 may have a conventional RF front end that may include one or more amplifiers, one or more filters, a mixer, and an analog to digital converter.

FIG. 2 shows a flow diagram illustrating a method of selecting a subset of N among N antennas receiving / transmitting N signals according to the present invention. The method has a plurality of steps 30, 32, 34, 36 and 38. In step 30, the method is started and variables are initialized. A variable or set of variables representing a hypothetical set of antennas is initialized in such a way that the hypothetical set has N antennas. The auxiliary variable n is set to zero. This auxiliary variable n is used to control the number of times steps 32 and 34 are executed.

  Thereafter, in step 32, the next antenna to be removed from the assumed set of antennas is determined and the auxiliary variable n is increased by one. The antenna to be removed next is an antenna having a maximum communication capacity (throughput) of the assumed set of the antenna after the removal of the antenna. For the next antenna to be removed, for example, for each antenna in the assumed set of antennas, calculate the resulting capacity after removal of the antenna and select the antenna or antennas that produce the highest capacity Can be determined. Alternatively, a capacity reduction due to antenna removal can be calculated for each antenna in the hypothetical set, and the antenna that results in the smallest capacity reduction upon removal is selected.

  Next, in step 34, the antenna determined in step 32 is removed from the hypothetical set (representing variable / variables) of the antenna.

Next, in step 36, it is determined whether the auxiliary variable n is greater than ( N -N). If affirmative, steps 32 and 34 are performed ( N -N) times, and ( N -N) antennas are taken from the assumed set of antennas (initially had N antennas). Once removed, the method continues to step 38. However, if not, at least one other antenna must be determined and removed from the hypothetical set of antennas, so steps 32 and 34 are performed again.

  In step 38, the method ends and the variable / variables representing the hypothetical set of remaining antennas has N antennas. The desired subset corresponds to the remaining hypothetical set of N.

Coupling means 18 makes it possible to either switch even in the M in the M transmit antennas to the available M transmit chains 20. Similarly, the coupling means 24, makes it possible to switch to any of the N in the N receive antennas 22 for N receive chains 26 available. s [k] = (s ₁ [k],..., s _M [k]) ^T is to be transmitted with a code interval k ≧ 0 and M × 1 of the signal supplied to the transmission chain 20 X [k] = (x ₁ [k], ..., x _N [k]) Define ^T as the corresponding N × 1 vector of the received signal, where ( ^T ) is the matrix Represents transposition. First, assume a non-selective noisy channel so that the relationship between s [k] and x [k] can be written as
x [k] = √ (E _S ) Hs [k] + n [k] (1)
Here, E _S is the (average) signal energy per also contributes channel used in any of the receiving antennas from any transmitting antennas, n [k] is the average energy of each antenna of each complex dimension (N ₀ / 2) is an N × 1 vector of environmental noise, H is an N × M channel matrix, where the component H _{q, p} is between the p th transmit chain and the q th receive chain Specifies a complex-value memoryless channel. Assume additive white Gaussian environmental noise such that E {n [k] n [k] ^H } = N ₀ I _N , where E {•} is the mathematical expectation and I _N is It is an N × N unit matrix, and ( ^H ) indicates Hermitian conjugate.

The maximum throughput (capacity) of such a channel is measured in bits per channel use,
C (H) = log ₂ det (I _N + (E _S / N ₀ ) HH ^H ) (2)
Where det (·) represents the determinant. In general, the purpose of the antenna selection procedure is to make M transmissions ( N receptions) out of the total available M transmissions ( N receptions) so that the throughput (2) is maximized. It is to select an antenna. The H is defined as N × M matrix describing the memoryless channel between the M transmit antennas and N receive antennas (assuming the antenna all with appropriate transmit / receive chains). The antenna selection problem here corresponds to the selection of the N × M sub-block H of the N × M matrix H that maximizes equation (2). A brute force approach to this problem as proposed in the above document is a thorough maximization of equation (2) over all possible N × M sub-blocks of H. This approach, however, is too cumbersome when M and / or N are relatively large. In the following, a computationally efficient suboptimal selection algorithm is described.

First, a fixed subset of M antennas is selected at the transmitter ( M = M makes sense if the transmitter has no channel information) and N available antennas. Assume that any set of N antennas in can be adaptively selected at the receiver in view of the N × M channel matrix H information. The latter matrix is obtained during the channel estimation stage when all N receive antennas (a subset) are connected in series to the N available front ends. According to the principles of the present invention, ( N− N) receive antennas are then removed so that each time, one antenna that causes the smallest reduction in the capacity according to equation (2) is removed. Next, focus on the implementation of this idea.

Note that removal of a single receive antenna is equivalent to suppression of a single row of matrix H. And H _p is the p th row of this matrix is the made of the remaining (N -1) rows of H (N -1) × M matrix

Outside 1

を示す。式（２）及び幾らかの単純な代数により、前記通信路

Indicates. According to equation (2) and some simple algebra, the channel

Outside 2

に対応する容量は、以下のように書き表されることができる。

The capacity corresponding to can be written as:

Note that the removal of the p-th row results in a capacity reduction reflected by the second term on the right side of equation (3). Hence, the optimal selection of (N -1) number of receiving antennas from among the N maximizes (3), or equivalently
H _p (I _M + (E _S / N ₀ ) H ^H H ) ⁻¹ H p ^H (4)
Yields p that minimizes.

In the general case where N < N and M = M, ( N− N) antennas will then have a minimum reduction in capacity of (3) or equivalently a minimum of (4) each time. Removed so that the resulting single antenna is removed. H, in careful (e.g. second stage to the removed receive antennas should be replaced by excluding submatrix columns corresponding, H is

Outside 3

により置き換えられる）。このような手順を効率的に実施するためには、（４）の逆行列に対する計算上効率的な更新を必要とする。このような更新は、正則なエルミート行列Ａ及び同じ次元のベクトルxに関連する関係
(A-xx^H)^-1=A^-1+A^-1x(1-x^HA^-1x)^-1x^HA^-1 （５）
により達成されることができ、ここで、Ａは、前の段階において利用された反転行列を表し、xは、√(E_S/N₀)掛ける前の段階において除去された前記通信路行列の転置された列である。N個の中からN個の受信アンテナを選択するアルゴリズムの擬似言語記述が、下に与えられる。

Replaced by In order to carry out such a procedure efficiently, a computationally efficient update to the inverse matrix of (4) is required. Such updates are related to a regular Hermitian matrix A and a vector x of the same dimension.
(A-xx ^H ) ^-1 = A ^-1 + A ^-1 x (1-x ^H A ^-1 x) ^-1 x ^H A ^-1 (5)
Where A represents the inverse matrix utilized in the previous stage, and x is the channel matrix removed in the previous stage multiplied by √ (E _S / N ₀ ). This is a transposed column. Pseudo language description of the N algorithms for selecting N receive antennas out of are given below.

Set H ← H , i ← (1, ..., N ) and compute B = (I _N + (E _S / N ₀ ) H ^H H) ^-1 .
For n = 1 to ( N -N) (n = 1 to ( N -N))
Begin
Find

Outside 4

such that（以下のような）

Update（更新）

If n<(N-N)（もしn<(N-N)ならば）
Begin（開始）
Update（更新）

End（終了）
End（終了）

such that

Update

If n <( N -N) (if n <( N -N))
Begin
Update

End
End

First, the channel matrix H and the vector i are initialized, i.e., H is equal to the N × M channel matrix H , i is equal to the 1 × N vector containing the indices of all N antennas. Is done. Vector i represents an assumed set of antennas (with N antennas initially). Furthermore, during initialization, the auxiliary variable B (the middle part of equation (4)) is calculated. The calculated value of this variable will be used during the calculation of the communication capacity during the first iteration of the algorithm.

The algorithm then performs ( N -N) iterations, and in each iteration, first the antenna to be removed first (ie

Outside 5

）が決定され、この後に、前記アンテナは、ベクトルiから対応するアンテナのインデックス

) Is determined, after which the antenna is indexed by the corresponding antenna from vector i

Outside 6

を除去することにより前記アンテナの仮定セットから除去される。

Is removed from the assumed set of antennas.

Outside 7

は、（Bの事前に計算された値を使用することにより）前記アンテナの仮定セットの残り全てのアンテナpに対して前記スループット／容量減少の式（４）を計算することにより決定される。

Is determined by calculating the throughput / capacity reduction equation (4) for all remaining antennas p of the hypothetical set of antennas (by using a pre-calculated value of B).

Outside 8

は、除去により最小のスループット／容量減少を生じる（換言すると、除去により最高の残りのスループット／容量を生じる）アンテナ（又は複数のアンテナの１つ）に対応する。

Corresponds to the antenna (or one of the plurality of antennas) that results in minimal throughput / capacity reduction upon removal (in other words, removal yields the highest remaining throughput / capacity).

  It is known that it is also possible to calculate the capacity / throughput of the remaining hypothetical set after removal of the respective antenna in each iteration for all antennas of the hypothetical set. However, calculating the capacity / throughput difference instead of the actual capacity is less complex and more computationally efficient.

  The channel matrix H and auxiliary variable B are updated at each iteration of the algorithm (except for the last iteration) to prepare for the next iteration. The update of the channel matrix H is the antenna just removed

Outside 9

に対応する行の除外を伴う。

With the exclusion of the row corresponding to.

  Finally, after completion of the algorithm, the resulting 1 × N vector i contains the index of the selected receive antenna.

It will be readily appreciated that this algorithm can also be applied to select transmit antennas (ie, when N = N and M > M). For this reason, it is shown that the equation (3) of the channel capacity is invariant with respect to the Hermite conjugate of the channel matrix. Look at the first line of (3). Hence, the algorithm proposed above, the initialization H ← H to H ← H ^H, a I _M to I _N, N to M and N after replacing the M that is readily available Can do. Pseudo language description of the modified algorithm from among the M resulting for selecting M transmit antennas is given below.

Set H ← H ^H , i ← (1, ..., M ) and compute B = (I _N + (E _S / N ₀ ) H ^H H) ^-1 .
For n = 1 to ( M -M) (from n = 1 to ( M -M))
Begin
Find

Outside 10

such that（以下のような）

Update（更新）

If n<(M-M)（もしn<(M-M)ならば）
Begin（開始）
Update（更新）

End（終了）
End（終了）

such that

Update

If n <( M -M) (if n <( M -M))
Begin
Update

End
End

  Note that the channel information at the transmitter 12 is essential for selecting the transmit antenna. This information may be supplied in different ways. One possibility is to use a feedback link from the receiver 14 to the transmitter 12. The receiver 14 uses this feedback link to communicate the acquired channel parameters to the transmitter 12. Other options may be available in time division duplex (TDD) mode, where the same carrier frequency is used for both downlink and uplink. In such a case, each site acquires the parameters of the propagation communication path between the sites during the reception stage. Due to electromagnetic wave propagation interactions, the channel parameters obtained during the reception phase are considered to be the same as the channel parameters required to achieve antenna selection in the subsequent transmission phase. Can do. The appropriate manner of supplying channel information to the transmitter 12 depends on the system requirements and the type of time frequency resource allocation.

であり、ここで、N×M行列のセットH[0],...,H[L]は、（近似）有限の因果的な（causal）通信路インパルス応答を特定する。周波数選択性通信路の容量は、

により与えられ、ここで、H(e^i2πf)=Σ_lH[l]e^-i2πflは、通信路周波数応答である。再び、M個のアンテナの固定サブセットは、前記送信器において選択され、N個のアンテナの中の任意のN個の受信アンテナのセットは、N×M行列の通信路応答H[0],...,H[L]の情報を鑑みて、前記受信器において適応的に選択されることができる。明らかに、（７）の直接的な計算は、少数の送信及び受信アンテナに対してでさえも厄介すぎる。的確な基準（７）は、２つの見地に基づき単純化され得る。 The algorithm proposed above is effective for memoryless channels. In the following, a similar algorithm for frequency selective channels will be revealed. The frequency selectivity of a wireless channel is usually due to multipath propagation that results in intersymbol interference. Often, the width of the propagation delay appears to be a reasonably diverse code rate. Such a channel can be accurately approximated by a finite impulse response (FIR) linear filter with a moderate number of taps. In these cases, the memoryless channel model (1) is expanded as follows:

Where the set of N × M matrices H [0],..., H [L] identifies (approximate) finite causal channel impulse responses. The capacity of the frequency selective channel is

Where H (e ^i2πf ) = Σ _l H [l] e ^−i2πfl is the channel frequency response. Again, the fixed subset of M antennas is selected at the transmitter, the N pieces of any set of N receive antennas in the antenna, the channel response H [0] of the N × M matrix,. .., H can be adaptively selected in the receiver in view of the information of [L]. Clearly, the direct calculation of (7) is too cumbersome even for a small number of transmit and receive antennas. The exact criterion (7) can be simplified based on two aspects.

First, Equation (7) is rewritten by Wiener-Masani theorem as follows:
C (H) = log ₂ det (D) (8)
Where D is the positive explicit spectral density matrix function
(I _M + (E _S / N ₀ ) H (e ^i2πf ) ^H H (e ^i2πf )), f∈ (0, 1)
Is the M × M innovation covariance matrix resulting from the causal minimum phase spectral decomposition of.

であることに注目する。 Secondly,

Note that

を提案する。 The first term on the right side of (9) includes the autocorrelation of the channel impulse response, while the remaining terms include only the cross-correlation. In view of the substantial decorrelation between coefficients corresponding to different delay taps, the first term will be more dominant than the other terms. Based on this perspective, approximate

Propose.

Hereinafter, the following notation is used.
H = [H _{1 ,:} [0] ^T , ..., H _{1 ,:} [L] ^T , ..., H _{N ,:} [0] ^T , ..., H _{N ,:} [L] ^T ] ^T
H = [ H _{1 ,:} [0] ^T , ..., H _{1 ,:} [L] ^T , ..., H _{N ,:} [0] ^T , ..., H _{N ,:} [L] ^T ] ^T (11)

を生じる。 Approximation (9) is

Produce.

The latter representation is similar to the previously proposed representation of throughput for memoryless channels (flat fading). The difference is that N (L + 1) x M matrix H continuous (L + 1) x M blocks ( N (L + 1) x M matrix H (L + 1) x M blocks) receive the same The fact is that it corresponds to different taps on the antenna. Hence, removal of a single antenna means removal of the corresponding (L + 1) × M block rather than a single row as in the case of a memoryless channel. Therefore, corresponding extensions of equations (3) and (5) are required. Based on these extensions, can be enhanced version of the algorithm for selecting N receive antennas out of N pieces of the previously mentioned (i.e. for frequency selective channel) is obtained, this pseudo language description Presented below.

Set H ← H , i ← (1, ..., N ) and compute B = (I _M + (E _S / N ₀ ) H ^H H) ⁻¹ .
For n = 1 to ( N -N) (n = 1 to ( N -N))
Begin
Find

Outside 11

such that（以下のような）

Update（更新）

If n<(N-N)（もしn<(N-N)ならば）
Begin（開始）
Update（更新）

End（終了）
End（終了）

such that

Update

If n <( N -N) (if n <( N -N))
Begin
Update

End
End

In this algorithm, H _p represents an (L + 1) × M block spanning rows (p−1) (L + 1) +1 to p (L + 1) of H. Note that the complexity of this algorithm increases significantly with the number of taps (L + 1). In fact, every stage of the algorithm calculates ( N− n + 1) determinants and one inverse matrix of size (L + 1) × (L + 1). Only a few important taps of the channel impulse response to the antenna selection can be taken into account to keep L small.

The algorithm can be configured to select a transmit antenna (N = N and M > M). Again, the invariance of the channel capacity with respect to the Hermite conjugate of the channel matrix is used. It is only necessary to modify the definition (11) as follows.
H = [H:, ₁ [0], ..., H:, ₁ [L], ..., H:, _M [0], ..., H:, _M [L]] ^H
H = [ H:, ₁ [0], ..., H:, ₁ [L], ..., H:, _M [0], ..., H:, _M [L]] ^H (13 )

A pseudo-language description of the resulting modified algorithm for selecting M transmit antennas out of M under frequency selective channel conditions is given below.

Set H ← H , i ← (1, ..., M ) and compute B = (I _N + (E _S / N ₀ ) H ^H H) ^-1 .
For n = 1 to ( M -M) (from n = 1 to ( M -M))
Begin
Find

Outside 12

such that（以下のような）

Update（更新）

If n<(M-M)（もしn<(M-M)ならば）
Begin（開始）
Update（更新）

End（終了）
End（終了）

such that

Update

If n <( M -M) (if n <( M -M))
Begin
Update

End
End

3 and 4 show several graphs illustrating the performance of the method according to the invention. Consider a scenario where the transmitter 12 uses M = 4 transmit antennas 16 and each transmit antenna 16 is coupled to a transmit chain 20 (ie, M = M) and the receiver 14 is N = 4 receive chain 16. The number of receiving antennas 22 is N = 8 (FIG. 3) and N = 16 (FIG. 4). Assume a Rayleigh flat fading channel and a completely uncorrelated transmit / receive antenna. In other words, the components of the channel matrix H are modeled as zero mean circular complex Gaussian variables that are distributed equally equally with variance (1/2) for each complex dimension. For the resulting subset from the various selection methods, an outage rate of 10% and an outage capacity for 1% was obtained in 10,000 independent simulation trials, and the resulting graph is Shown in FIGS. A solid line with a circular mark indicates the optimal subset degradation capacity that results from the prior art exhaustive search approach. Such an exhaustive search is an M × M matrix

Outside 13

の行列式を計算する必要があり、これは、M=M=4、N=4及びN=16の場合に、４×４行列の１８２０個の行列式になる。星印を有する実線は、上で提案された最初の前記アルゴリズム（即ちフラットフェージング状況下でN個の中からN個の受信アンテナを選択するアルゴリズム）によって決定されたサブセットの劣化容量を表す。この手順の複雑さは、M×M行列により定義される(2M-M+1)(M-M)/2の二次形式の計算により支配される。前記上の例において、二次形式の数は１７４である。ベンチマーク目的のために、ランダムに選択されたN=4個のアンテナから成るサブセットの性能は三角形の印を有する実線により表される。本発明による前記方法は、最適な選択と比較して無視してもよい損失を生じることが理解されることができる。代わりに、前記ランダムな選択の利得は、所望の劣化率に応じて変化し、低い及び中位のＳＮＲにおいて５０％に接近する。

Need to be calculated, which is 1820 determinants of a 4 × 4 matrix when M = M = 4, N = 4 and N = 16. The solid line with an asterisk represents the degraded capacity of the subset determined by the first algorithm proposed above (ie, the algorithm that selects N receive antennas out of N under flat fading conditions). The complexity of this procedure is dominated by a quadratic form calculation of (2 M −M + 1) ( M −M) / 2 defined by an M × M matrix. In the above example, the number of secondary forms is 174. For benchmark purposes, the performance of a randomly selected subset of N = 4 antennas is represented by a solid line with a triangle mark. It can be seen that the method according to the invention results in negligible losses compared to optimal selection. Instead, the random selection gain varies depending on the desired rate of degradation, approaching 50% at low and medium SNRs.

  The scope of the invention is not limited to the specifically disclosed embodiments. The present invention is implemented with each new characteristic and each combination of characteristics. Any reference signs do not limit the scope of the claims. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim. The use of the word “one” before an element does not exclude the presence of a plurality of such elements.

1 shows a block diagram of a transmission system 10 according to the present invention. Fig. 2 shows a flow diagram illustrating a method according to the invention. 2 shows several graphs illustrating the performance of the method according to the invention. 2 shows several graphs illustrating the performance of the method according to the invention.

Claims (6)

A method of selecting a subset of N in the N antennas to N signals received / transmitted, starting from the assumption set of N antennas, the antenna from the hypothetical set ( N− N) removals, the removal being performed such that the capacity of the hypothetical set after removal of the antenna has a maximum value, and the subset corresponds to the remaining hypothetical set of N antennas. How to choose by doing. A receiver for receiving N signals, the receiver, and a N receive antennas and N receive chains, N is greater than N, the receiver further the N has a coupling means for selectively coupling the receive chain to a subset of N among the N antennas, the coupling means, starting from the assumption set of the N antennas, the assumption set antenna the (N -N) times removed from, the removal capacity of the hypothetical set after removal of the antenna is performed to have a maximum value, the subset, the remaining of said of N antennas A receiver configured to select the subset of N antennas by corresponding to a hypothetical set. A transmitter for transmitting M signals, the transmitter, and a M transmit antennas and M transmit chains, M is greater than M, the transmitter further the M the transmit chain comprises a coupling means for selectively coupling to a subset of M in the M antennas, the coupling means, starting from the assumption set of the M antennas, the assumption set antenna the (M -M) times removed from, the removal capacity of the hypothetical set after removal of the antenna is performed to have a maximum value, the subset, the remaining of the of M antennas A transmitter configured to select the subset of M antennas by corresponding to a hypothetical set.   A transmission system comprising the receiver according to claim 2 and / or the transmitter according to claim 3. A method of receiving N signals by a receiver having N larger than N and having N receiving antennas and N receiving chains,
Wherein an N number of steps of selecting a subset of N in the antenna, said starting from the N hypothesis set of antenna, the antenna was (N -N) times removed from the hypothetical set, the Removal is performed such that the capacity of the hypothetical set after removal of the antenna has a maximum value, and the subset is selected by corresponding to the remaining hypothetical set of N antennas;
Coupling the N receive chains to the subset of N antennas;
Having a method. A method of transmitting M signals by a transmitter having M larger than M and having M transmit antennas and M transmit chains,
Wherein a M number of steps of selecting a subset of M in the antenna, said starting from the assumption set of M antennas, the antenna from the hypothetical set to (M -M) times removed, the Removal is performed such that the capacity of the hypothesis set after removal of the antenna has a maximum value, and the subset is selected by corresponding to the remaining hypothesis set of M antennas;
Coupling the M transmit chains to the subset of M antennas;
Having a method.

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